SOLUTIONS1. Concentration Units

A. Molarity; mole fraction; % m/m; molality

2. Principles of Solubility

A. solute-solvent interactions; effect of T & P;

3. Colligative Properties

A. VP lowering; BP elevation; FP depression; osmotic pressure

B. Molar mass determination from colligative prop

4. Colligative Properties of Electrolytes

0. Review:

• solution =homogeneous mixture of solute and solvent.

• solute = substance being dissolved

• solvent = substance doing the dissolving

• Solutions exist as gases, liquids, or solids

• Air = 78% N2, 21% O2, others (e.g., Ar 0.1%)

• nickel coin = 25% Ni, 75% Cu

Concentration Units

1. Molarity (M)

•

• M1V1 = M2V2 (dilution)

2. Mole Fraction

• (XA + XB +.... = 1)

1. Mass Percent (% m/m)

• % (m/m) =

• parts per million =

Concentration Units (con’t)

3. Molality (m)

• used for colligative properties

• m

4. Conversions Between Concentration Units

When the Original Concen. Is Start With

• molarity (M) 1.00 L

• mole fraction (X) 1 mol (solute + solvent)

• molality (m) 1000 g solvent

• mass percent 100 g solution

Concentration Units (con’t)

Conversions Between Concentration Units

When the Original [] Is Start With

• Molarity (M)

𝑀=𝑚𝑜𝑙𝑠𝑜𝑙𝑢𝑡𝑒𝐿𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛

Start with 1.00 L solution

Concentration Units (con’t)

Conversions Between Concentration Units

When the Original [] Is Start With

• Mole Fraction (XA)

𝑋 𝐴=𝑚𝑜𝑙 𝐴

𝑚𝑜𝑙 𝑡𝑜𝑡𝑎𝑙=𝑛𝐴

𝑛𝑇𝑂𝑇𝐴𝐿

Start with 1 mol (solute + solvent)

Concentration Units (con’t)

Conversions Between Concentration Units

When the Original [] Is Start With

• Mass Percent, % (m/m)

% (𝑚𝑚 )= 𝑚𝑎𝑠𝑠𝑠𝑜𝑙𝑢𝑡𝑒𝑚𝑎𝑠𝑠𝑡𝑜𝑡𝑎𝑙𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑥100 %

Start with 100 g solution

% = *100; parts per thousand = *1000; ppm = * 106; etc.

Concentration Units (con’t)

Conversions Between Concentration Units

When the Original [] Is Start With

• molality (m)

𝑚=𝑚𝑎𝑠𝑠 𝑠𝑜𝑙𝑢𝑡𝑒𝑘𝑔 𝑠𝑜𝑙𝑣𝑒𝑛𝑡

Start with 1000 g solvent

Example – Concentrated HCl

The amount of HCl in concentrated solution = 37.7%

A. What are %’s of HCl & water in concentrated HCl?

HCl = 37.7%

H2O = 100.0 – 37.7 = 62.3%

Example

2. What is the molality of HCl? (37.7%)

A. Start with 100.0 g solution (37.7% HCl / 62.3% H2O)

B. Convert mole HCl to kg H2O

Example

3. What is the molarity of HCl?

A. Start with 100.0 g solution (again)

B. Convert mole HCl to kg H2O

• you have already calc’d 1.03 mol HCl

C. Find to sol’n volume (density = 1.19 g/mL)